Consider one further experiment with the piston-cylinder arrangement of Figure 4. Suppose thecylinder contained 1 lbm of ice at 0°F, 14.7 psia. When heat is transferred to the ice, thepressure remains constant, the specific volume increases slightly, and the temperature increasesuntil it reaches 32°F, at which point the ice melts while the temperature remains constant. In thisstate the ice is called a saturated solid. For most substances, the specific volume increases duringthis melting process, but for water the specific volume of the liquid is less than the specificvolume of the solid. This causes ice to float on water. When all the ice is melted, any furtherheat transfer causes an increase in temperature of the liquid. The process of melting is alsoreferred to as fusion. The heat added to melt ice into a liquid is called the latent heat of fusion.